fix(js): make setAttributeNS/getAttributeNS/removeAttributeNS namespace-aware

The three NS methods ignored the namespace: setAttributeNS stored the qualified
name against the non-namespaced store and getAttributeNS/removeAttributeNS
looked up by local name only, so a namespaced attribute was not addressable by
(namespace, localName) — getAttributeNS(xlink, 'href') returned null.

Record the namespace on the attribute and add namespace-aware DOM ops that match
by (namespace, localName), where the local name is the attribute name after any
prefix (so both setAttributeNS-created 'xlink:href' and parser-created 'href'
resolve). The non-namespaced getAttribute/serialization paths are untouched, and
getAttributeNS(null, name) still reads plain attributes.

Fixes #503

crates/obscura-js/src/ops.rs

@@ -378,6 +378,36 @@ fn op_dom_inner(state: &OpState, cmd: String, arg1: String, arg2: String) -> Str
             });
             "true".into()
         }
+        // Namespace-aware attribute ops. arg2 packs the pieces with a NUL:
+        //   get/remove: "<namespace>\0<localName>"
+        //   set:        "<namespace>\0<qualifiedName>\0<value>"
+        "get_attribute_ns" => {
+            let nid = arg1.parse::<u32>().unwrap_or(0);
+            let (ns, local) = arg2.split_once('\0').unwrap_or(("", arg2.as_str()));
+            let val = dom
+                .with_node(NodeId::new(nid), |n| n.get_attribute_ns(ns, local).map(|s| s.to_string()))
+                .flatten();
+            serde_json::to_string(&val).unwrap_or("null".into())
+        }
+        "set_attribute_ns" => {
+            let nid = arg1.parse::<u32>().unwrap_or(0);
+            let mut parts = arg2.splitn(3, '\0');
+            let ns = parts.next().unwrap_or("");
+            let qualified = parts.next().unwrap_or("");
+            let value = parts.next().unwrap_or("");
+            if !qualified.is_empty() {
+                dom.with_node_mut(NodeId::new(nid), |n| {
+                    n.set_attribute_ns(ns, qualified, value.to_string())
+                });
+            }
+            "true".into()
+        }
+        "remove_attribute_ns" => {
+            let nid = arg1.parse::<u32>().unwrap_or(0);
+            let (ns, local) = arg2.split_once('\0').unwrap_or(("", arg2.as_str()));
+            dom.with_node_mut(NodeId::new(nid), |n| n.remove_attribute_ns(ns, local));
+            "true".into()
+        }
         "set_inner_html" => {
             let nid = match arg1.parse::<u32>() {
                 Ok(n) if n > 0 => n,

crates/obscura-js/src/runtime.rs

@@ -1317,6 +1317,34 @@ mod tests {
         rt
     }
 
+    #[test]
+    fn set_attribute_ns_is_retrievable_by_namespace_and_local_name() {
+        let mut rt = setup_runtime("<html><body></body></html>");
+        let v = rt
+            .evaluate("(function(){var s=document.createElementNS('http://www.w3.org/2000/svg','svg'); s.setAttributeNS('http://www.w3.org/1999/xlink','xlink:href','#g'); return s.getAttributeNS('http://www.w3.org/1999/xlink','href');})()")
+            .unwrap();
+        assert_eq!(v, serde_json::json!("#g"));
+    }
+
+    #[test]
+    fn remove_attribute_ns_removes_by_namespace() {
+        let mut rt = setup_runtime("<html><body></body></html>");
+        let v = rt
+            .evaluate("(function(){var s=document.createElementNS('http://www.w3.org/2000/svg','svg'); s.setAttributeNS('http://www.w3.org/1999/xlink','xlink:href','#g'); s.removeAttributeNS('http://www.w3.org/1999/xlink','href'); return s.getAttributeNS('http://www.w3.org/1999/xlink','href');})()")
+            .unwrap();
+        assert_eq!(v, serde_json::json!(null));
+    }
+
+    #[test]
+    fn get_attribute_ns_reads_plain_attributes_with_null_namespace() {
+        // Backward-compat: getAttributeNS(null, name) still reads a plain attr.
+        let mut rt = setup_runtime(r#"<html><body><div id="d" title="hi"></div></body></html>"#);
+        let v = rt
+            .evaluate("document.getElementById('d').getAttributeNS(null,'title')")
+            .unwrap();
+        assert_eq!(v, serde_json::json!("hi"));
+    }
+
     #[test]
     fn test_document_title() {
         let mut rt = setup_runtime("<html><head><title>Test</title></head><body></body></html>");